A process for grinding and coloring wood chips.
U.S. Pat. No. 5,308,653 of Rondy discloses a process for preparing a colored wood product, such as mulch. In the first step of the process of this patent, comminuted wood is fed into a screw conveyor having a first end and a second end, wherein the screw conveyor has a helical auger disposed axially and in close fitting relationship to the internal surface within a generally closed channel, and with a feed port near the first end and a discharge end near the second end, the helical augur being capable of being rotated by a drive means; in this step, the comminuted wood is fed through the feed port into the first end of the conveyor. In the second step of the process of this patent, the comminuted wood is contacted with an aqueous color-imparting solution containing at least one color-imparting agent therein for sufficient time to disperse the color-imparting solution onto the surfaces of the comminuted wood to create a colored wood product, such contact occurring at least at the feed port through a feed port nozzle means substantially transversing the feed port and providing a gravity feed sheet of the color imparting solution from a longitudinal slot formed therein. In the third step of the process of this patent, the augur is rotated so that the colored wood product is drawn from the first end to the second end, during which time excess color-imparting solution is drained away from the colored wood product, thereby drying the colored wood product. In the last step of the process, the dried colored wood product is discharged from the screw conveyor (via a discharge chute) and further dried, if necessary. The entire disclosure of this United States patent is hereby incorporated by reference into this specification.
The process of the Rondy patent produces a colored mulch patent with a substantially non-uniform particle size distribution and non-uniformly colored particles. Furthermore, the colored mulch produced by the Rondy patent is not intensely colored.
It is an object of this invention to provide a process for producing a colored mulch which has intense color and which is substantially more uniform than the prior art colored mulch products.
In accordance with this invention, there is provided a process for producing a colored mulch in which wood is ground by a mill until a compact is formed with at least 80 weight percent of the particles smaller than 4.0 inches, the compact thus formed is sieved to produce a sieved product, the sieved product is then sprayed with a colorant solution while it is being conveyed by a multiplicity of augers to produce a first colored sieved product, the first colored sieved product is immersed in a bath of colorant solution to produce a second colored sieved product, and the second colored sieved product is removed from the bath by a multiplicity of augers and dried.